1. Field of the Invention
This invention relates to motor driven film winding-up and shutter charging devices for cameras, and more particularly to motor driven winding-up devices for cameras provided with a clutch mechanism operating to cut off the supply of driving torque from the driving source to the film winding-up system, when the exposed film is wound-up by the length of one frame.
2. Description of the Prior Art
In the past, in the art of motor driven winding-up devices for cameras, there have been proposed a wide variety of one-frame film advancement controls. For example, when the exposed film is advanced by one frame, a signal is taken out by utilized the perforations provided in the film. Then, it is by this signal that the clutch mechanism is rendered inoperative so that driving torque from an electric motor or like driving power source is no longer transmitted to a film transport system. Therefore, such motor driven winding-up device has a requirement that, in order to allow for the recurrent film winding operation after the completion of each exposure, the clutch mechanism be coupled again in itself, rendering it possible to transmit motion of the driving power source to the film transport system. According to the prior art, therefore, the clutch mechanism is arranged to recouple either in response to depression of the release button, or by utilizing the action of the shutter operating member. With such arrangements, however, in the former case, the depressing force of the release button must be increased and, therefore, when taking a photograph, the photographer will experience some discomfort. Further, in application to electromagnetic release cameras where only an electrical switch suffices for initiation of a camera operation, it is required that the above-described transmission control in mechanical form be provided in isolation, thereby giving rise to a drawback that the usefulness of the electromagnetic release is diminished. Also, in cameras operating with the torque supply from a driving power source such as a motor, the timing of the start of rotation of the motor with the aforesaid recoupling must be strictly adjusted by the use of complicated means. Next, in the latter case where the aforesaid recoupling is effected by making use of the action of the shutter operating member, since the kinetic energy of the shutter member is generally small, the range of work of the shutter operating member except for the recoupling of the clutch mechanism is necessarily very limited. Since a motorized camera has, for example, a circuit changeover switch, and this switch also must be actuated, a drawback results in that there is a great loss in the accuracy and reliability of control of the operation of these parts. This tendency is so prominent, particularly in lens shutters (including so-called semi-open type shutters) where the kinetic energy is very small, that an increase in the work of the shutter operating member will call for an influence on the aperture characteristics of the shutter blades. Thus, it has been very difficult to make the shutter operating member so as to serve as an actuator for the various members and the switch.
Turning to the camera of the type having such a motor driven winding-up device, in more detail, where the driving torque from the electric motor or other suitable driving source is transmitted to a spool on which the film is wound-up, and when the film is advanced by one frame, the clutch mechanism is cut off to stop the film from being further wound-up. However, the following problem further arises. That is, in the conventional practice, such camera when switched from the winding-up to the rewinding mode is made compatible with a smooth rewinding operation, by rendering the aforesaid clutch mechanism inoperative. Then, when switching from the rewinding to the winding mode, this switching operation is followed automatically by the clutch mechanism returning to the operative position. Therefore, the stoppage of the film in the rewinding operation results in the restraint of the spool from further rotation in the reverse direction. Then, if the leader of the film is yet left on the spool, it is very troublesome to detach the film from the spool. With such situation overlooked, when the photographer is unloading the cartridge from the camera, the exposed film often will be pulled out and fogged.